Is your present motherboard giving you problems somehow? Is so, how exactly? I'm not sure I'd advocate switching to a newer motherboard if the current one is causing you zero problems.

Odds are, a quick survey from this forum on mobo choices will get you mostly Intel chipset suggestions. But as you are, you're only one video card away from an SLI setup. Was that something you wanted to keep as an option?

Beyond that, how serious of an overclocker are you? Once you crack the $200 mark, most of what the more expensive boards give you are more BIOS options. But some people just hate screwing with that sort of stuff, and even the latest midrange boards should have no trouble supporting your current overclock, especially if you're switching the watercooling.